Intercropping: Minimize Your Effort While Maximizing Yields
By Pam Dawling
Tangible benefits come to gardeners who practice intercropping. Also known as relay planting, interplanting, or undersowing, this technique is a version of companion planting where the second crop is planted while the first is still growing. Don’t worry about whether the two crops benefit each other — just look at how the gardener benefits! Growers are drawn to intercropping because it’s a way to increase the land’s productivity while also boosting the diversity of insects and other beneficial organisms. Other efficiencies include having two crops share a single row cover or irrigation system.
There are several intercropping models. Sometimes a small, quick-growing crop is planted between slower growing crops to use the space not yet needed by the slower crop. Sometimes a tall crop and a sprawling crop are planted together. Sometimes a later, slower crop is given a chance to get started before the first crop is cleared. The first crop may act as what’s known as a “nurse crop,” providing shade or soil-holding roots for the second crop. Note that the intercrop should never be allowed to dominate the main crop, and weeds shouldn’t be allowed to compete with either crop. High soil fertility is needed to make this system work.
Early Spring Intercropping
Intercropping peas and spinach in spring makes good use of garden resources. As legumes, peas don’t need high levels of nitrogen in the soil. So, in soils with good fertility, you can interplant peas in a standing crop without adding any more compost.
Because spring heats up quickly here in central Virginia, we have a short season for peas — we have to start them as early as possible, or we won’t harvest any. We plant a single or double row of peas in the middle of each spinach bed, and then we care for the two crops together. The crops share row cover, warmer soil, cultivation, compost, and, above all, space. By intercropping these two, you can eliminate one tilling and still have a bed that’s doubly productive. Plus, planting them together will help keep your attention on the need to weed and harvest both crops. The spinach will gradually give way to the peas as spring advances.
The trick is to plan ahead. In fall, we plant four rows of spinach in one 4-foot-wide bed. When winter arrives, we cover the beds with sturdy double hoops and thick row cover to save the spinach from getting weather-beaten. In spring, we transplant more spinach plants into additional beds.
When you plant the spinach, make sure to leave a slightly wider central space between the inner rows for the peas — less than a whole row’s worth because peas are a vertical crop. We use the Bed Preparation Rake with Row Markers from Johnny’s Selected Seeds — it’s a worthwhile investment for making consistently parallel rows, and also makes faster hoeing possible.
We interplant the existing spinach with peas in spring. Because the beds are already warm under the row cover, we can sow earlier than we could in uncovered soil. We aim to sow our peas on March 1, or whenever the forsythia blooms. Shelling peas can be sown earlier than snap peas, which are more vulnerable to rotting in cold soil, probably because the seed is higher in sugars.
Before planting, we soak the pea seeds overnight, hoe and weed the spinach, and harvest the bigger leaves from the inner rows of spinach. We make one or two shallow furrows for the peas down the middle of the spinach beds, sow the peas, and replace the row cover.
By the time the peas need to be staked, we’re also ready to uncover the spinach to delay its desire to bolt — and we need the row cover elsewhere in the garden anyway. We harvest spinach leaves throughout the spring, about once a week per bed. We harvest whole spinach plants when they’re ready to bolt, and clear out all the spinach in April and May. Eventually we’re left with a bed of peas only. One year we fell behind with removing the bolting spinach, so we simply used the tall spinach flower stems to support the peas!
In early spring, you can interplant chard with lettuce or other fast-growing crops as a viable alternative to mulching. You should transplant the chard starts at the usual in-row spacing — about 16 inches between rows — and then transplant lettuces between the chard rows. Harvest the lettuce after about five weeks, before the chard gets big.
Late Spring and Early Summer Intercropping
You can interplant lettuce with peanuts, tomatoes, peppers, or other slower-growing crops to increase the productivity of an area and provide better habitat for one or both crops. Sow or transplant warm-weather crops into the center of beds of lettuce one month or more after direct seeding, or at the transplanting stage.
We’ve had great results by sowing a row of peanuts in the middle of a lettuce bed. The timing is a little tricky — we’re still fine-tuning it — so you should try this at least twice before deciding if it will work for you. We sow the peanuts into the middle of a bed with lettuce transplants around our average last frost date (April 29 to May 12). The ideal seems to be to plant regular-sized (not overgrown) lettuce transplants on the same day (or up to two weeks after) we sow the peanuts. We use romaine lettuces and small bibbs for these plantings, and avoid large, spreading leaf lettuces.
The peanuts do well so long as we remember they’re there and don’t mistake them for weeds and hoe them off while working our lettuce beds. (Back when we sowed peanuts in empty beds, the unusual, slow-to-emerge seedlings were hard for some of our newer crew to distinguish from the weeds.) During unseasonably warm springs, we spread shade cloth over the whole bed for the sake of the lettuce, and the peanuts still come up very nicely. In cooler springs, we use row cover. Lettuce will grow faster than peanuts in cool, wet springs, so we may have to harvest the inner rows of greens earlier than normal to prevent them from swamping the peanuts. We harvest all the lettuces before the peanuts grow large, leaving the latter plenty of space.
If you’ve researched companion planting, you’ll have learned that it’s usual for the yield of one or both crops to be lower than if they were grown alone in separate plots. In my experience, though, lettuce and peanuts do well together. I’ve also read studies that have shown intercropping transplanted lettuces with tomatoes won’t reduce lettuce yields or delay the date of first tomato harvest. But timing is critical: Lettuce sown immediately before the tomatoes are transplanted will have a significantly lower yield because the tiny lettuce seedlings cannot compete with faster-growing tomato plants.
Okra grows slowly until hot weather arrives. We sometimes take advantage of this, and the plant’s upright growth habit, to intercrop okra and early cabbage. On March 10, we plant cabbage starts in two rows in a 4-foot-wide bed, and on May 11, we transplant okra starts in a single row down the middle. The okra utilizes the open space in the middle of the bed. As the okra plants grow, we remove any outer leaves of the cabbage that might overshadow it. In late May and early June, we harvest the cabbage so the okra has room to grow to full size.
I’ve read of intercropping cucumbers and okra, giving each plant 3 feet of space. This takes advantage of the crops’ very different growth habits — sprawling cucumbers and upright okra — to harvest more food from the same piece of land. Some people claim that interplanting corn with vining squashes will deter raccoons and other critters, but I think it deters the garden crew, too!
Intercropping is an effective gardening method that will save space in your plots and make efficient use of your time by letting you take care of two crops at once. You can also use intercropping to get a cover crop established in a timely way that wouldn’t be possible if you waited for the food crop to be finished first. Just remember to build up your soil fertility to keep the interplanted crops growing and producing.
The Three Sisters
Squash, beans, and corn are an ancient garden partnership. Thousands of years ago, native peoples understood that planting these three crops together benefited both the plants and the soil. We know today that the crops complement one another nutritionally too. Learn more about intercropping squash, beans, and corn in Ancient Companion Planting: The Three Sisters.
Bio: Pam Dawling has grown vegetables at Twin Oaks Community in central Virginia for more than 25 years. She often presents workshops at Mother Earth News Fairs. You can find more from Pam on her blog, Sustainable Market Farming. Some of this material is from her book, Sustainable Market Farming, available in the Heirloom Gardener store.
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